One part swapped
Take one hydrogen off a chain. Put something else in its place.
Step 1 of 5
- Plain hydrogen caps the end — no group at all.
- Swap in –OH: the alcohol group.
- Swap in –CHO: the aldehyde group.
- Swap in –COOH: the acid group.
- Swap in –Cl: a chlorine group.
Put a group on the C₂H₅– chain. Read the family and the name.
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The rule
Swap the group on a chain's end and the family changes. The functional group decides the family.
A functional group is a group of atoms that sets the family. It decides how the substance behaves.
| Group | Family | Compound |
|---|---|---|
| –OH | Alcohol | Ethanol, C₂H₅OH |
| –CHO | Aldehyde | Propanal, C₂H₅CHO |
| –COOH | Carboxylic acid | Propanoic acid, C₂H₅COOH |
| –Cl | Haloalkane | Chloroethane, C₂H₅Cl |
Another group, >C=O, is inside a chain. It makes a ketone. Propanone is a three-carbon ketone.
The name counts every carbon, even the one inside the group. C₂H₅–CHO has 2 + 1 = 3 carbons, so it is propanal. CH₃–COOH has two carbons, so it is ethanoic acid.